But, I'm perhaps missing something: wouldn't moving 1.8 IQ points in an IQ distribution with a SD of 2.7 be a large effect? I tried researching whether a standardized beta is a measure of effect size, but got mixed results...

Depends what you mean. It is large in the standardized sense at the state-level. It is quite small at the individual level. Generally, I think it is more sensible to use the individual-level norms for interpretation. So, while you do find evidence that Republication majority states have lower IQs controlling for various factors, this effect is quite small. This is what would be expected because the individual-level literature on the topic finds only minor and inconsistent differences in IQ between preferred party, and conservative/liberal self-placements (depending on sample, measure, control variables etc.).

I don't see any updated version of the submission. As per standard practice, please create a repository on OSF for it and place (and update) the submission there. OSF is easy to use and free.